The United States and Japan will step up their defence cooperation to deal with the threat from nuclear-armed North Korea as tensions in East Asia remain high, officials from the two allies said on Thursday.

He said prisoners were frequently held beyond the date when they were due to be released on parole because of a lack of acceptable housing.

"There is an increasing need for supervised accommodation," he said.

"This is expensive, but it is less expensive than continued imprisonment or the consequences of further offending."

While noting everyone in the public sector was aware of the need for budgetary restraint, Justice Whelan called for the appointment of a second full-time member to manage the board's increasing workload.